A common problem encountered with natural and synthetic materials, particularly synthetic organic polymers, is their instability on exposure to light, atmospheric conditions and elevated temperatures, as well as the adverse effects exerted on the polymers by the minute amounts of catalyst residues often present in the synthetic polymers, which frequently lead to physical deterioration and color change. Over the years industry has resorted to the addition of a wide variety of antioxidants, ultraviolet light absorbers and heat stabilizing agents to the polymers but there is still exerted a continuing effort to find new materials that will accomplish the same or improved objectives without affecting other properties that may have a deleterious effect on manufacturing and processing operations. It is also known in industry that a compound that stabilizes against heat and/or oxygen degradation may not stabilize against light degradation in the same material, and vice versa. It is further known that a compound which exerts some form of stabilization in one type of material may be completely ineffective in another type of material. Thus, compounds are classified as antioxidants, light stabilizers, heat stabilizers, etc., depending upon the stabilizing effect a particular compound may have on a specific material or type of material. As a consequence, in many cases, mixtures of stabilizers are used to obtain desired protection against one or more forms of degradation.
In Rev. Macromal. Chem. Phys., C22(2), 169-203 (1982-1983), Dagonneau et al. published a review "Sterically Hindered Amines and Nitroxyls as Polymer Stabilizers" which includes conventional piperidine compounds among the stabilizers disclosed. However, none of the sterically hindered amines are silicon-based.
U.S. Pat. No. 4,535,113, issued to G. N. Foster et al. on Aug. 13, 1985, discloses the use of certain silicone compounds as additives to olefin polymers. Among the silicone compounds are the alkylaminosiloxy-containing materials as exemplified in Examples 7 to 10. However, there is no mention of any sterically hindered heterocyclic amines of the type used in this invention.
It has now been found that certain polysiloxanes containing a pendant sterically hindered aminoheterocyclic moiety attached to the siloxane chain stabilize synthetic polymers, particularly synthetic olefin polymers, against the deleterious effects caused by exposure to light and heat.